We identified number of records records. See Figure 1 for the PRISMA flow diagram. A total of 11 studies with data from 771 participants were eligible for inclusion.
Figure 1: PRISMA flow diagram
10 of the studies were RCTs, and 1 was a crossover RCT (Greene & Petruzzello, 2022). 8 of the 11 studies were included in the meta-analyses (Bryant et al., 2023; Huseth, 2021; Nordbrandt et al., 2020; Rosenbaum et al., 2015; Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b; Young-McCaughan et al., 2022). Meta-analysis was not feasible for 3 of the 11 studies (Crombie et al., 2021a; Greene & Petruzzello, 2022; Powers et al., 2015). These were synthesized descriptively without meta-analysis. Three of the studies provided follow-up PTSD outcome data which were insufficient for synthesis (Bryant et al., 2023; Voorendonk et al., 2023; Young-McCaughan et al., 2022). Three studies examined putative mediators but were only summarised descriptively (Crombie et al., 2021a; Powers et al., 2015; Whitworth et al., 2019b).
Study characteristics of the 8 studies included in the meta-analysis are summarized in Table 1. From these 8 studies, there were 9 eligible comparisons. One study presented findings from two independent comparisons, including a total of four distinct intervention groups (Young-McCaughan et al., 2022). One of the first authors published findings from two different but methodologically similar trials in the same year (Whitworth et al., 2019a; Whitworth et al., 2019b).
| Study | Year | N | Intervention | Comparison | PTSD tool | Trial registered | Exercise type | Exercise intensity | Intervention length | FU1 | FU2 | Country |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Bryant2023 | 2023 | 130 | exercise + therapy | attention control + therapy | CAPS-IV | yes | aerobic | high | 10 weeks | 34 weeks | NA | Australia |
| Voorendonk2023 | 2023 | 120 | exercise + therapy | attention control + therapy | PCL-5 | yes | mixed | moderate | 12 weeks | 26 weeks | NA | Netherland |
| Nordbrandt2020 | 2020 | 224 | exercise + TAU | TAU | HTQ | yes | mixed | moderate | 20 weeks | NA | NA | Denmark |
| Rosenbaum2014 | 2014 | 81 | exercise + TAU | TAU | PCL-4 | yes | mixed | high | 12 weeks | NA | NA | Australia |
| Young-McCaughan2022b | 2022 | 36 | exercise + therapy | therapy only | PCL-5 | no | aerobic | high | 8 weeks | 12 weeks | 32 weeks | USA |
| Huseth2022 | 2022 | 21 | exercise only | WLC | PCL-5 | no | aerobic | moderate | 8 weeks | NA | NA | USA |
| Young-McCaughan2022a | 2022 | 36 | exercise only | TAU | PCL-5 | no | aerobic | high | 8 weeks | 12 weeks | 32 weeks | USA |
| Whitworth2019a | 2018 | 30 | exercise only | attention control | PDS-5 | no | anerobic | high | 3 weeks | NA | NA | USA |
| Whitworth2019b | 2019 | 22 | exercise only | attention control | PDS-5 | no | anerobic | high | 3 weeks | NA | NA | USA |
Aerobic exercise = physical performance behaviour pattern that increases heart rate and respiration while using large muscle groups repetitively and rhythmically; anaerobic exercise = physical performance behaviour pattern that is performed in short intense bursts with limited oxygen intake; mixed exercise = combination of aerobic and anaerobic exercise. CAPS-IV = Clinician-Administered PTSD Scale - 4th edition; PCL-4 = PTSD Checklist - version 4; PCL-5 = PTSD Checklist version 5; HTQ = Harvard Trauma Questionnaire. TAU = treatment as usual.
Table 1: Study characteristics of the 8 studies included in the meta-analysis.
Study characteristics of the 3 studies not included in the meta-analysis are summarized in Table 2. From these 3 studies, there were 4 eligible comparisons.One study reported two comparisons (Greene & Petruzzello, 2022).
| Study | Year | N | Intervention | Comparison | Trial registered | Exercise type | Exercise intensity | Intervention length | Country |
|---|---|---|---|---|---|---|---|---|---|
| Crombie2021 | 2021 | 38 | exercise + extinction learning | attention control + extinction learning | yes | aerobic | moderate | 3 days | USA |
| Greene2022a | 2022 | 24 | exercise only | attention control | no | anaerobic | high | 130 min | USA |
| Greene2022b | 2022 | NA | exercise only | attention control | no | aerobic | moderate | 130 min | USA |
| Powers2015 | 2015 | 9 | exercise + therapy | therapy alone | yes | aerobic | moderate | 12 weeks | USA |
Aerobic exercise = physical performance behaviour pattern that increases heart rate and respiration while using large muscle groups repetitively and rhythmically; anaerobic exercise = physical performance behaviour pattern that is performed in short intense bursts with limited oxygen intake; mixed exercise = combination of aerobic and anaerobic exercise.
Table 2: Study characteristics of the 3 studies not included in the meta-analysis.
The specific intervention and comparison groups for the 11 eligible studies (0 comparisons) are presented in Table 3.
| Study | Intervention | Comparison | Exercise type | Therapy | TAU | Attention control |
|---|---|---|---|---|---|---|
| Bryant2023 | exercise + therapy | attention control + therapy | aerobic | exposure therapy | NA | static stretching |
| Voorendonk2023 | exercise + therapy | attention control + therapy | mixed | PE + EMDR | NA | guided (creative) tasks |
| Nordbrandt2020 | exercise + TAU | TAU | mixed | NA | combination: medical doctor, 1 to 2 sessions with social worker / psychologist | NA |
| Rosenbaum2014 | exercise + TAU | TAU | mixed | NA | combination: individual and group psychotherapy, pharmacotherapy | NA |
| Young-McCaughan2022b | exercise + therapy | therapy only | aerobic | imaginal exposure | NA | NA |
| Huseth2022 | exercise only | WLC | aerobic | NA | NA | NA |
| Young-McCaughan2022a | exercise only | TAU | aerobic | NA | self-care intervention delivering educational and instructional information | NA |
| Whitworth2018 | exercise only | attention control | anaerobic | NA | NA | videos on various educational topics (excluding exercise and mental health). |
| Whitworth2019 | exercise only | attention control | anaerobic | NA | NA | videos on various educational topics (excluding exercise and mental health). |
| Crombie2021 | exercise + extinction learning | attention control + extinction learning | aerobic | extinction learning | NA | NA |
| Greene2022a | exercise only | attention control | mixed | NA | NA | remained sedentary in the lab |
| Greene2022b | exercise only | attention control | aerobic | NA | NA | remained sedentary in the lab |
| Powers2015 | exercise + therapy | therapy alone | aerobic | prolonged exposure | NA | NA |
Table 3: Specific interventions for all the included studies
The results of the risk of bias (ROB) assessment per domain and study for the primary outcome, PTSD symptom severity, is presented in Figure 2. Nine studies reported PTSD outcome data post-intervention. Two studies did not report PTSD outcome data (Crombie et al., 2021a; Greene & Petruzzello, 2022). Overall, five studies were rated as high, three studies as some concerns, and one was rated as low risk of bias. High risk of bias was mainly due to deviations from intended intervention (D2)(Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), missing outcome data (D3)(Rosenbaum et al., 2015; Voorendonk et al., 2023; Whitworth et al., 2019a; Whitworth et al., 2019b), and selection of reported results (D5)(Voorendonk et al., 2023; Young-McCaughan et al., 2022).
Figure 2 Risk of bias for PTSD symptom severity
For the studies included in the meta-analyses, the earliest study was performed in 2014, while the most recent study was performed in 2023. The median sample size across the studies was 36 participants per study. The median of the mean participant age was 37 years (ranging from 29 to 50 years).
8 studies provided data for PTSD symptom severity and contributed 9 effect measures to the PTSD symptom severity meta-analysis. The summary for PTSD symptom severity is shown in Figure 3.
Figure 3: Meta-analysis of the effects of exercise on PTSD symptom severity.
The meta-analysis found no significant difference in PTSD symptom severity between exercise and comparison groups (SMD = -0.08 , 95% CI: -0.24 , 0.07). Low heterogeneity was found as suggested by the prediction interval which is only slightly wider than the confidence interval.
We explored whether heterogeneity could be potentially explained by differences in study-level characteristics using subgroup analyses and meta-regressions. The following characteristics were explored as sources of heterogeneity for the primary outcome, PTSD symptom severity:
Exercise intensity (moderate intensity or high intensity)
Specific exercise type (aerobic or anaerobic or mixed)
Exercise augmented by treatment as usual (TAU)/therapy (exercise only or exercise + therapy/TAU)
Intervention length (weeks)
There was no significant difference in PTSD symptom severity between studies with moderate intensity and those with high intensity exercise groups (Figure 4). However, visual inspection of the forest plot suggests the effect is larger in the high intensity exercise subgroup.
Figure 4: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise intensity
The were no significant difference in PTSD symptom severity between studies of aerobic exercise, anaerobic exercise, or mixed (Figure 5).
Figure 5: Sub-group analysis of the effects of exercise on PTSD symptom severity by specific exercise type
There was no significant difference in PTSD symptom severity between studies investigating exercise alone and those investigating TAU/therapy augmented by exercise (Figure 6). However, visual inspection of the forest plot suggests the effect is larger for exercise alone compared with an inactive comparison group than for the studies that augmented psychotherapy and TAU with exercise.
Figure 6: Sub-group analysis of the effects of exercise on PTSD symptom severity by exercise alone or TAU/therapy augmented by exercise
Overall, there is no strong evidence that the intervention length affected the treatment effect. The meta-regression analysis yielded a coefficient of 0.02 (95% CI: -0.01, 0.05).
Figure 7: Meta-regression of the effects of exercise on PTSD symptom severity by intervention length
8 studies provided data for treatment dropout, and contributed 9 effect measures to the treatment dropout meta-analysis. The forest plot for the risk of treatment dropout is shown in Figure 8.
Figure 8: Meta-analysis of the dropout rates between the intervention and control groups
There is no evidence of a difference in treatment dropout between exercise and comparison groups (RR = 1.28 , 95% CI: 0.67 , 2.45) and there is large heterogeneity, as shown by the prediction interval (0.16 to 10.15).
We examine the robustness of the findings for the primary outcome by excluding studies with high risk of bias. 3 studies included in the meta-analyses were rated as low or some concerns. When restricting the analysis to studies with moderate or low risk of bias, the effect of exercise on PTSD symptoms severity is SMD = -0.06 (95% CI: -0.27 , 0.14). For reference, the main effect size for the primary outcome is SMD = -0.08 (95% CI: -0.24 , 0.07), so the results do not change substantially.
Figure 9: Meta-analysis of the effects of exercise on PTSD symptom severity when excluding studies with high risk of bias
The forest plot below shows the meta-analysis results of the primary outcome ordered by the precision of the studies. It seems that smaller studies showed larger effects favouring the intervention.
Figure 10: Forest plot of the meta-analysis results of the primary outcome ordered by the precision of the studies
The primary outcome was efficacy in reducing overall PTSD symptom severity in patients with PTSD. The summary of the evidence on PTSD symptom severity outcome for PTSD is reported below.
| Source of evidence | Summary of the association | Bias due to study limitations | Bias due to reporting bias | Bias due to indirectedness | Bias due to other reasons |
| Exercise intervention vs comparison group | n = 9 , k = 700 , SMD = -0.08, 95%CI: -0.24, 0.07 | Overall, five studies were rated as high, three studies as some concerns, and one was rated as low risk of bias. High risk of bias due to to deviations from intended intervention, missing outcome data, and selection of reported results. | Two studies rated as high risk of bias | what here | Lack of blinding of participants and outcomes assessors. |